Methods and systems for minimally invasive posterior arch expansion

ABSTRACT

Provided are methods and systems for enlarging a spinal canal of a vertebra. Using the methods and systems disclosed the spinal canal of the vertebra is enlarged by cutting the posterior arch portion of the vertebra to create one or two implant receiving spaces in the posterior arch portion. The cutting of the posterior arch portion is completed through a minimally invasive approach. Once cut, the detached portion of the posterior arch portion is repositioned and an implant is positioned in the implant receiving space of the posterior arch portion to thereby enlarge the spinal canal such that the spinal cord is no longer compressed. The insertion of the implant is also completed through a minimally invasive approach.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/327,928 filed on Dec. 16, 2011, which claims the benefit ofU.S. Provisional Application Ser. No. 61/424,127 filed Dec. 17, 2010,the disclosures of both of which are hereby incorporated by reference asif set forth in their entirety herein.

BACKGROUND

The spine is susceptible to various medical conditions that reduce thearea within the vertebra available for the spinal cord and nerve roots.For instance, spinal stenosis is a condition in which the spinal canalnarrows and compresses the spinal cord and nerve roots. Spinal stenosismay be caused by many medical conditions, such as the calcification andthickening of the ligaments of the spine (e.g., from deposits of calciumsalts), enlargement of bones and joints, formation of osteophytes (bonespurs), a herniated (bulging) disk, and diseased bone or tumors mayresult in an ingrowth into the spinal cord area. Thus, the amount ofanatomical space available for the spinal cord and nerve roots thatemanate from the spinal cord can be reduced, which often results inlower back pain as well as pain or abnormal sensations in theextremities. Spinal stenosis may affect the cervical, thoracic or lumbarspine.

Surgical procedures are available for treating spinal stenosis byrelieving pressure on the spinal cord through posterior arch expansion.The conventional surgical procedures typically involve first making anincision in the back and stripping muscles and supporting structuresaway from the spine to expose the posterior portion of the vertebralcolumn. Once exposed, the spinal canal may be widened (i.e. theposterior arch may be expanded), either by removing the lamina(laminectomy) or by cutting the lamina and then spreading it apart withan implant (laminoplasty). The invasive nature of conventional posteriorarch expansion methods often result in significant post-operative painand long patient recovery times.

SUMMARY

In accordance with an embodiment, a minimally invasive posterior archexpansion system is configured to expand a spinal canal. The system caninclude an access assembly that is configured to form a minimallyinvasive access path to an implant receiving space defined by first andsecond opposed posterior arch surfaces. The system can further include aspreading device and an implant. The spreading device is configured toextend through the minimally invasive access path of the access assemblyand engage the implant receiving space to thereby widen the implantreceiving space such that the first and second posterior arch surfacesmove away from each other. The implant is configured to be implanted inthe implant receiving space. The system further includes an insertertool that is configured couple to the implant and is configured toextend through the minimally invasive access path of the access assemblyto thereby insert the implant into the implant receiving space.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofa preferred embodiment of the application, will be better understoodwhen read in conjunction with the appended drawings. For the purposes ofillustrating the minimally invasive procedure and systems of the presentapplication, there is shown in the drawings several embodiments. Itshould be understood, however, that the application is not limited tothe precise arrangements and instrumentalities shown. In the drawings:

FIG. 1A is a top plan view of a vertebra having a narrowed spinal canal,the vertebra including a posterior arch portion having a lamina and aspinous process separating the lamina into first and second portions;

FIG. 1B is a top plan view of the vertebra shown in FIG. 1A expanded inaccordance with an embodiment, the vertebra having first and secondimplant receiving spaces formed in the first and second portions of thelamina and first and second implants implanted into the first and secondimplant receiving spaces to thereby expand the spinal canal;

FIG. 1C is a top plan view of the vertebra shown in FIG. 1A expanded inaccordance with another embodiment, the vertebra having a hinge formedin the first portion of the lamina, and implant receiving space formedin the second portion of the lamina, and an implant implanted into theimplant receiving space to thereby expand the spinal canal;

FIG. 1D is a top plan view of the vertebra shown in FIG. 1A expanded inaccordance with another embodiment, the vertebra having first and secondhinges formed in the first and second portions of the lamina, an implantreceiving space formed in the spinous process, and an implant implantedinto the implant receiving space to thereby expand the spinal canal;

FIG. 2A is a perspective view of an access assembly including a K-wire,a dilator disposed over the k-wire, and a cannula disposed over thedilator, the cannula defining a passageway that forms a minimallyinvasive access path to the posterior arch portion such as to thelamina;

FIG. 2B is a top plan view of the cannula shown in FIG. 2A;

FIG. 3A is a side elevation view of a cutting tool system constructed inaccordance with an embodiment, the cutting tool system including a firstcutting tool that is configured to cut partially into the lamina tothereby form a hinge in the lamina as shown in FIG. 1C;

FIG. 3B is a side elevation view of the cutting tool system shown inFIG. 3A further including a second cutting tool configured to cutthrough the lamina or the spinous process to thereby form the implantreceiving space;

FIG. 4A is a perspective view of an implant assembly constructed inaccordance with an embodiment, the implant assembly including an implantinserter tool and an implant coupled to the implant inserter tool, theimplant inserter tool configured to expand the implant receiving spaceas the implant is inserted into the implant receiving space;

FIG. 4B is an expanded perspective view of a distal portion of theimplant inserter tool shown in FIG. 4A, the implant inserter tool havinga spreading device that includes distal engagement portions that areconfigured to engage the implant receiving space;

FIG. 4C is an expanded front elevation view of the distal portion of theimplant inserter tool shown in FIG. 4B, the engagement portions of thespreading device having a first position whereby the engagement portionsare separated by a first distance so as to be inserted into the implantreceiving space;

FIG. 4D is an expanded front elevation view of the distal portion of theimplant inserter tool shown in FIG. 4C, the engagement portions of thespreading device having a second position whereby the engagementportions are separated by a second distance that is greater than thefirst distance to thereby widen the implant receiving space so that theimplant can be implanted into the implant receiving space;

FIG. 5A is a perspective view of the implant shown in FIG. 4A;

FIG. 5B is a top plan view of the implant shown in FIG. 5A;

FIG. 5C is a side elevation view of the implant shown in FIG. 5A;

FIG. 5D is a perspective view of an implant in accordance with anotherembodiment, the implant including a lip and a plurality of teeth thatare configured to engage the lamina;

FIG. 6A is a top sectional view of the first cutting tool of the cuttingassembly extending through the passageway of the cannula of the accessassembly to thereby form the hinge in the first portion of the lamina;

FIG. 6B is a top sectional view of the second cutting tool of thecutting assembly extending through the passageway of the cannula of theaccess assembly to thereby form the implant receiving space in thesecond portion of the lamina;

FIG. 6C is a top sectional view of the implant assembly extendingthrough the passageway of the cannula of the access assembly such thatthe engagement portions of the inserter tool are inserted into theimplant receiving space;

FIG. 6D is a top sectional view of the implant assembly after theimplant has been advanced into the implant receiving space and theimplant receiving space has been widened by the inserter tool;

FIG. 6E is a top sectional view of the implant secured within theimplant receiving space to thereby retain the widened implant receivingspace in the widened position;

FIG. 7A is a schematic view of a cutting tool system constructed inaccordance with another embodiment, the cutting tool system including acutting tool that produces ultrasonic waves configured to cut into theposterior arch portion;

FIG. 7B is a schematic view of a cutting tool system constructed inaccordance with another embodiment, the cutting tool system including acutting tool defined as an abrasive wire that is configured to cut intothe posterior arch portion;

FIG. 7C is a schematic view of a cutting tool system constructed inaccordance with another embodiment, the cutting assembly including acutting tool defined as a rib cutter that is configured to cut into theposterior arch portion;

FIG. 8 is a side perspective view of an implant constructed inaccordance with another embodiment, the implant including a body and apair of engagement members that extend from the body, each engagementmember defining two wings that are configured to be coupled to theposterior arch portion;

FIG. 9 is a side perspective view of an implant constructed inaccordance with another embodiment, the implant including a threadedbody and a pair of engagement members, at least one of the engagementmembers is configured to move along the threaded body to thereby affixthe implant to the posterior arch portion;

FIG. 10A is a side perspective view of an implant constructed inaccordance with another embodiment, the implant including a body, afirst engagement member, and a mandrel extending through the body;

FIG. 10B is a side perspective view of the implant shown in FIG. 10Aafter the mandrel has been translated proximally to thereby form asecond engagement member;

FIG. 11A is a perspective view of an implant constructed in accordancewith another embodiment, the implant including an expandable body havingfirst and second threaded portions coupled together with an expansionmechanism such that rotation of the expansion mechanism causes theimplant to expand;

FIG. 11B is a perspective view of the implant shown in FIG. 11A in anexpanded configuration or position;

FIG. 12A is a perspective view of an implant constructed in accordancewith another embodiment, the implant including an expandable body thathas a balloon such that expansion of the balloon causes the implant toexpand;

FIG. 12B is a perspective view of the implant shown in FIG. 12A in anexpanded configuration or position;

FIG. 13 is a perspective view of an implant constructed in accordancewith another embodiment, the implant including an oblong body and isexpandable such that when inserted into the implant receiving space ofthe posterior arch portion, the implant may be rotated to thereby widenthe spinal canal;

FIG. 14A is a perspective view of an implant constructed in accordancewith another embodiment, the implant including an expandable body havingfirst and second frames coupled together by first and second members, anexpansion mechanism coupled to one of the members, such that rotation ofthe expansion mechanism causes the frames to move away from each otherand the implant to expand;

FIG. 14B is a perspective of the implant shown in FIG. 14A in anexpanded configuration or position;

FIG. 15A is a perspective view of an implant constructed in accordancewith another embodiment, the implant including an expandable bodydefined as a deformable O-ring such that compression of the O-ringcauses the implant to expand;

FIG. 15B is a perspective view of the implant shown in FIG. 15A in aflattened or expanded configuration or position;

FIG. 16 is a schematic view showing a lamina cut so as to provide animplant receiving space that defines a pair of keel cuts extending intothe posterior arch portion;

FIG. 17A is a side elevation view of an implant constructed inaccordance with another embodiment, the implant including engagementmembers configured as keels capable of engaging the keel cuts defined bythe implant receiving space of the posterior arch portion shown in FIG.16, the implant further including a rotatable member that is configuredexpand the implant upon rotation of the rotatable member by 90 degrees;

FIG. 17B is a side elevation view of the implant shown in FIG. 17A in anexpanded configuration or position;

FIG. 18A is a side elevation view of an implant constructed inaccordance with another embodiment, the implant including engagementmembers configured as keels capable of engaging the keel cuts defined bythe implant receiving space of the posterior arch portion shown in FIG.16, the implant further including first and second body portions coupledtogether by a pair of rotating members such that translation of thefirst body portion with respect to the second body portion causes theimplant to expand;

FIG. 18B is a side elevation view of the implant shown in FIG. 18A in anexpanded configuration or position;

FIG. 19A is a perspective view of an implant constructed in accordancewith another embodiment, the implant including an expandable body thatdefines a deformable O-ring that is locked in a compressed position witha locking pin;

FIG. 19B is a perspective view of the implant shown in FIG. 19A in anexpanded position after the pin has been removed;

FIG. 20 is a side elevation view showing an implant constructed inaccordance with another embodiment, the implant having stops that areconfigured to prevent the implant from being over inserted into theimplant receiving space of the posterior arch portion shown in FIG. 16;

FIG. 21 is a perspective view of an implant constructed in accordancewith another embodiment, the implant having a flat paddle member and ascrew that extends from the paddle member, the screw is configured toengage the posterior arch portion, and the paddle member is configuredto be attached to the lamina with a fastener;

FIG. 22 is a perspective view of an implant constructed in accordancewith another embodiment, the implant including a paddle member having ahinged portion;

FIG. 23A is a perspective view of an implant assembly constructed inaccordance with another embodiment, the implant assembly including aninserter tool configured as a threaded rod, and an implant configured tobe engaged by the threaded rod to thereby couple the implant to thethreaded rod; and

FIG. 23B is a perspective view of the inserter tool shown n FIG. 23A.

DETAILED DESCRIPTION

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right”, “left”, “lower” and “upper”designate directions in the drawings to which reference is made. Thewords “inwardly” or “distally” and “outwardly” or “proximally” refer todirections toward and away from, respectively, the geometric center ofthe system and related parts thereof. The words, “anterior”,“posterior”, “superior,” “inferior” and related words and/or phrasesdesignate preferred positions and orientations in the human body towhich reference is made and are not meant to be limiting. Theterminology includes the above-listed words, derivatives thereof andwords of similar import.

The spine is comprised of a series of vertebra that are stacked on topof each other from the bottom of the skull to the pelvis. Each vertebrais composed of several parts that act as a whole to surround and protectthe spinal cord and nerves. In particular and in reference to FIG. 1A,each vertebra 10 includes a spinal canal 14 that is defined by ananterior portion 18, opposed lateral portions 22, and a posterior archportion 26. The spinal canal 14 protects a spinal cord 28 that passesthrough the spinal canal 14 of each vertebra 10. As shown, the anteriorportion 18 is composed of a vertebral body 30 that is the main portionof the vertebra 10. The opposed lateral portions 22 of the vertebra 10are pedicles 34 which are cylinder-shaped projections that extend outfrom the posterior side of the vertebral body 30. The posterior archportion 26 is composed of a lamina 38 and a spinous process 42 thatextends out from a midline of the lamina 38. The lamina 38 acts as aroof of the spinal canal 14 and provides support and protection for theposterior side of the spinal cord 28.

In reference to FIG. 1A, the spinal canal 14 of the vertebra 10 shown,has narrowed and the spinal cord 28 that runs through the spinal canal14 is impinged upon by the surrounding boney parts that define thespinal canal 14. As a result, extreme discomfort may be experienced bythe patient. The spinal canal 14 can thus be widened through posteriorarch expansion, as shown in FIGS. 1B, 1C, and 1D, to remove theimpingement on the spinal cord 28. The posterior arch expansion caninclude for example cutting through the lamina (i.e. laminoplasty) orcutting through the spinous process.

To widen the spinal canal 14, the lamina 38 can be cut on one or bothsides of the spinous process 42 to form one or two corresponding implantreceiving spaces 46 (e.g., at least one implant receiving space 46) inthe lamina 38, as shown in FIG. 1B. That is once cut, the lamina 38 candefine opposed first and second posterior arch surfaces 47 a and 47 a,and the implant receiving space 46 can be defined between the first andsecond posterior arch surfaces 47 a and 47 a. The spinal canal 14 may beenlarged by inserting an implant 50 into each implant receiving space 46of the lamina 38. As shown in FIG. 1B, once the implants 50 are fullyinserted into the implant receiving spaces 46, the spinal canal 14 isexpanded and the spinal cord 28 is no longer pinched. The lamina 38 canbe approached, for instance, in a posterior approach I₁ or amedial—lateral approach I₂.

Alternatively, the spinal canal 14 may be widened by cutting the lamina38 to form a single implant receiving space 46 as shown in FIGS. 1C and1D. For instance, the lamina 38 can be cut only a portion of the waysuch as half way through a first portion 62 of the lamina 38 on one sideof the spinous process 42 to form a hinge 54, and all of the way througha second portion 66 of the lamina 38 on the other side of the spinousprocess 42 to form the implant receiving space 46. A first portion 62 ofthe lamina 38 is then rotated about the hinge 54 and the implant 50 isinserted into the implant receiving space 46 to thereby widen the spinalcanal 14. As will be appreciated from the description herein, theposterior arch expansion system can be configured to cut partially intoor through the lamina 38 at one or both sides with respect to thespinous process 42.

The spinal canal 14 may also be widened with a single implant receivingspace 46 by cutting through the middle of the spinous process 42 asshown in FIG. 1D, such that the spinous process 42 defines the implantreceiving space 46. For instance hinges 54 can be formed on both sidesof the spinous process 42 in the first and second portions 62 and 66 ofthe lamina 38. The first and second portions 62 and 66 of the lamina 38that are disposed between the spinous process 42 and the hinges 54 canthen be rotated about their respective hinges 54, so as to widen theimplant receiving space 46 and correspondingly widen the spinal canal14. The implant 50 can then be inserted into the implant receiving space46 to fix the spinal canal 14 in its widened configuration. It should beappreciated, however, the first and second portions 62 and 66 of thelamina may be weak enough that hinges 54 do not have to be formed.

For each of the above identified procedures, the lamina 38 can beaccessed, cut, and widened using a minimally invasive approach so as tolimit damage to the patient's surrounding tissue and muscle, therebyfurther limiting patient recovery time. The minimally invasive approachcan be performed using a minimally invasive posterior arch expansionsystem that includes at least one of an access assembly such as accessassembly 59 shown in FIGS. 2A-2B, a cutting tool system, such as cuttingtool system 98 shown in FIGS. 3A-3B, and an implant assembly, such asimplant assembly 181 shown in FIGS. 4A-4D. The posterior arch expansionsystem or one or more of its components can be included in a kit thatincludes multiple implants and instruments.

Referring to FIGS. 2A-2B, the access assembly 59 is configured topenetrate the tissue to create or otherwise form a minimally invasiveaccess path to the first portion 62 of the lamina 38. For instance andas shown in FIG. 2A, the access assembly 59 includes a K-wire 60 thatcan be inserted at a location proximate to the lamina 38. The accessassembly 59 can further include one or more dilators 64 that can bepassed over the wire 60 to thereby incrementally widen the access pathto the lamina 38 until the access path is sized as desired. As shown inFIGS. 2A and 2B, the access assembly 59 can further include an accessmember, illustrated as a cannula 70 that is slid over the outer dilator64 toward the first portion 62 of the lamina 38 once the access path hasreached the desired size. As shown, the cannula 70 includes an elongatebody 74 that is elongate along a longitudinal axis C. The cannula 70further includes a passageway 75 that extends through the body 74 alongthe longitudinal axis C and defines a cross-section, such as a diameterD. The body 74 defines a first proximal end 71 that is configured to beexternal from the patient's body once the cannula 70 has been fullyinserted into the access path, and an opposed distal end 73 that isspaced from the proximal end 71 along the longitudinal axis C, and isconfigured to be disposed proximate to the proximal portion of thevertebra, for example at the lamina 38. In embodiments where a vertebraof the cervical spine is being operated on, the cannula 70 can have adiameter between about 10 mm and about 25 mm, and in embodiments where avertebra of the lumbar spine is being operated on, the cannula 70 canhave a diameter between about 15 mm and about 50 mm. In this way, thecannula 70 provides a minimally invasive access path for the procedure.It should be appreciated, however, that the minimally invasive accesspath can have other cross sectional dimensions so long as minimal traumais caused to the surrounding muscle of the vertebra being operated on.Moreover, it should be appreciated that the access assembly 59 can beconfigured to penetrate the tissue to create or otherwise form aminimally invasive access path to other portions of the posterior archportion 26 such as to the spinous process 42.

As shown in FIG. 2A, the dilators 64 may include a cylindrical body 78having a tapered distal end 82. The tapered end 82 allows the tissue toexpand as the dilators 64 are inserted. It should be appreciated,however, that the dilators 64 may include other configurations. Forexample, the dilators 64 can include oblong body so long as the dilatorsincrementally increase in diameter, and are configured to be slid overeach other until the desired workspace or access path cross sectionaldimension is achieved.

It should be appreciated that other methods and procedures may beperformed using the posterior arch expansion system or componentsthereof so as to create the minimally invasive access path to thevertebra. For example, the tissue can be cut toward the vertebra using ascalpel or any suitable alternative access member such as a retractorcan be inserted through the soft tissue to access the vertebra.

Referring now to FIG. 3A, the cutting tool system 98 is configured tocut into the posterior arch portion 26 of the vertebra, such as into thelamina 38. In accordance with the illustrated embodiment, the cuttingtool system 98 includes a first cutting tool 100 that is configured tobe inserted into the passageway 75 of the cannula 70 and advanceddistally through the passageway 75 toward the vertebra such as towardthe first portion 62 of the lamina 38 along the longitudinal axis C ofthe tube body 74. The first cutting tool 100 may be configured to cutinto the lamina 38 to a certain depth so as to not cut all the waythrough the lamina 38. For example, the first cutting tool 100 may be arotary tool such as a mill having a longitudinal body 104, a cutting tip108 at a distal end of the body 104, and a stop member in the form of ashoulder 112 proximate to the cutting tip 108. The shoulder 112 canextend radially out from the tool body 104 at a location that limits thedepth at which the cutting tool 100 can advance into the lamina 38. Forexample, the shoulder 112 can abut the lamina 38 so as to create aninterference that prevents the first cutting tool 100 from advancingfurther into the lamina 38. Therefore during use, as the cutting tool100 is advanced down the cannula 70, the cutting tip 108 cuts into thelamina 38 until the shoulder 112 abuts or otherwise engages an outersurface of the lamina 38. At this point, the first cutting tool 100 willno longer cut into the lamina 38 thereby preventing the cutting tool 100from cutting all the way through the lamina 38. For instance, thecutting tool 100 can define a cutting depth between the shoulder 112 andthe distal end of the cutting tip 108 that is between about 0.75 mm toabout 1.25 mm, though it should be appreciated that the cutting depthcan be sized as desired depending on the surgical procedure and thepatient anatomy. Thus, the first cutting tool 100 can cut into, but notthrough, the lamina 38 so as to form the hinge 54 that is configured toopen the lamina 38 in the manner described above. It should beappreciated, that one or more hinges 54 may be formed depending on whatprocedure is being performed. It should be further appreciated that thefirst cutting tool 100 can be configured to cut into, and entirelythrough, the lamina 38 on either side of the spinous process 42 as shownin FIG. 1B. Moreover, it should be appreciated that the first cuttingtool 100 can be configured to cut into, and entirely through, thespinous process 42.

Once the hinge 54 has been created (if a hinge 54 is desired), then asecond access path to the second portion 66 of the lamina 38 can also becreated. The second access path may be created using the same methodsand tools that are configured to create the first access path to thelamina 38. For example, the second access path may also be made usingthe access assembly 59 shown in FIGS. 2A and 2B. While the first accesspath was made to provide access to the first portion 62 of the lamina 38located on a first side of the lamina 38, the second access path is madeto provide access to a second portion 66 of the lamina 38 located on asecond side of the lamina 38. That is, the first and second openings areconfigured to provide access to the lamina 38 on either side of thespinous process 42. As with the first access path, once the desired size(e.g., diameter) of the second access path is achieved, the cannula 70can be slid over the dilators to thereby provide a minimally invasivework space for the second portion 66 of the lamina 38. It should beappreciated, however, that the access assembly 59 can include a secondcannula so that two minimally invasive work spaces can be provided forthe first and second portions of the lamina 38 at the same time.

As shown in FIG. 3B, the cutting tool system 98 can include a secondcutting tool 150 that is configured to be inserted into the passageway75 of the cannula 70 and is advanced toward the second portion 66 of thelamina 38 along the longitudinal axis C of the tube body. The secondcutting tool 150 may be a rotary tool such as a mill having alongitudinal body 154, and a cutting tip 158 at a distal end of the body154. The second cutting tool 150 may be coupled to the tube 70 outsideof the access path so that the second cutting tool 150 can be advancedin precise increments. In this way the second cutting tool 150 will beable to cut completely through the lamina 38 to create an implantreceiving space 46 of the lamina 38, while not inadvertently cutting thespinal cord. It should be appreciated that while the cutting tool system98 is described as having first and second cutting tools 100 and 150,the cutting tool system 98 can include a single cutting tool that isconfigured to cut the lamina as described.

The cutting tool system 98, including the first and second cutting tools100 and 150 can include an visualization device such as an endoscope.The endoscope can be attached to or separate from the first and secondcutting tools 100 and 150. The endoscope can be configured to extendthrough passageway 75 along with the cutting tools 100 or 150 or canextend through the tissue external to the passageway 75.

Now referring to FIGS. 4A-4D, the implant assembly 181 includes animplant 170 and an inserter tool 180 that is configured to insert theimplant 170 into the implant receiving space 46 of the lamina after theimplant receiving space 46 has been created. For instance, after theimplant receiving space 46 has been created, the second cutting tool 150can be removed from the tube 70 and the inserter tool 180 and implant170 can subsequently be advanced through the passageway 75 of the tube70 toward the implant receiving space 46. Referring to FIG. 4A, theinserter tool 180 includes a housing 182 and an elongate pusher 184 thatextends through the housing 182. The elongate pusher 184 includes athreaded rod 185, a handle 186 at a proximal end of the rod 185, and abiasing member 188 at a distal end of the rod 185 that is configured toeither grip or push against the implant 170. The handle 186 may be anystructure configured to be gripped by a user, while the biasing member188 may be any structure capable of holding and/or pushing the implant170. For example, in the illustrated embodiment, the biasing member 188is an abutment surface 189 that is configured to push or otherwise movethe implant 170 distally. It should be appreciated, however, that thebiasing member 188 can include other configurations such as a threadedmember, or a suction member so as to be able to grip and removably affixthe implant 170 to the inserter tool 180. The threaded rod 185 isconfigured to engage internal threads defined by the housing 182 suchthat the pusher 184 can be incrementally translated.

As shown, the implant assembly 181 can also include a spreading device192 that extends distally from the housing 182 and around the implant170. The spreading device 192 is configured to engage the implantreceiving space 46 and then spread the posterior arch portion 26 such asthe lamina 38 so as to expand or otherwise widen the implant receivingspace 46 such that the implant 170 may be placed within the implantreceiving space 46. The spreading device 192 includes a first arm 196and a second arm 200 that extend distally from the housing 182 onopposite sides of the pusher 184. As shown, each arm 196 and 200includes a first portion 201 that extends radially outward, away fromthe pusher 184, and a second angled portion 202 that extends radiallyinward toward the other of the angled portions 202. In this way, thefirst and second arms 196 and 200 curve around the implant 170, thentoward each other until they terminate at a point distal to the implant170. As shown, the arms 196 and 200 terminate such that the ends of thearms 196 and 200 are proximate to each other so as to be able to fitinto and engage the implant receiving space 46 of the lamina 38. Forexample, the arms 196 and 200 can further include engagement portions203 that extend from the second angled portions 202. The engagementportions 203 can be flat panels 205 that abut each other and areconfigured to engage the implant receiving space 46 of the posteriorarch portion and provide a force direct or indirect against theposterior arch surfaces. For example, the engagement portions 203 cancontact respective posterior arch surfaces to thereby widen the implantreceiving space.

As shown, the first and second arms 196 and 200 each define a rail 206that extends along a portion of the length of the arm toward theengagement portion 203. The rails 206 can be defined by the secondangled portions 202 and the engagement portions 203 of the first andsecond arms 196 and 200 and are configured to guide the implant 170 andthe biasing member 188 toward the engagement portions 203. In theillustrated embodiment, the rails 206 are slots 207 that extend throughthe arms 196 and 200 and are elongate along the length of the secondangle portions 202. It should be appreciated, however, that the rails206 can include other configurations as desired, so long as the railsare configured to guide the implant 170 toward the engagement portions203.

As shown in FIG. 4B, the spreading device 192 further includes at leasttwo stops 208 that extends laterally out from the engagement portions203. The stops 208 are spaced from a distal end of the engagementportions 203 and are configured to limit the insertion depth of theengagement portions 203 into the implant receiving space 46. In theillustrated embodiment the stops 208 are projections that extend outfrom the engagement portions 203 on opposite sides of the rails 206.

As shown in FIGS. 4C and 4D, the spreading device 192 can have a firstor engaging position as shown in FIG. 4C and a second or expandedposition as shown in FIG. 4D. While in the first position, theengagement portions 203 are separated from each other by a firstdistance L₁ and while in the second position the engagement portions 203are separated from each other by a second distance L₂ that is greaterthan the first distance L₁. It should be appreciated that while in thefirst position the engagement portions 203 can abut each other such thatthe first distance L₁ is 0 mm. As the implant 170 is guided down therails 206 the implant 170 forces the engagement portions 203 away fromeach other to thereby increase the distance between the engagementportions 203 from the first distance to the second distance.

Now referring now to FIGS. 5A-5C the implant 170 includes an implantbody 171 having a leading end 173 a with respect to insertion into theimplant receiving space 46, and a trailing end 173 b opposite theleading end 173 a with respect to a central longitudinal axis 177,opposed sides 175 that extend between the leading and trailing ends 173a and 173 b, and opposed upper and lower surfaces 183 a and 183 b,respectively. The leading end 173 a can define a different length thanthe trailing end 173 b. For instance, the leading end 173 a defines alength that is less than that of the trailing end 173 b in accordancewith the illustrated embodiment. Accordingly, the sides 175 can betapered (or angularly offset with respect to the longitudinal axis 177)between the leading and trailing ends 173 a and 173 b. For instance, oneor both of the sides 175 can be angled inwards (e.g., toward each other)along a direction from the trailing end 173 b toward the leading end 173a. Thus, the implant body 171 can be generally wedge shaped, andconfigured to be inserted into the implant receiving space 46, such thatthe sides 175 are configured to abut complementary surfaces of theposterior arch portion 26 such as the lamina 38 that at least partiallydefine the implant receiving space 46. In this way the sides 175 candefine first and second bone engaging surfaces that are configured tourge against the first and second posterior arch surfaces. The implant170 can further define at least one aperture 190 that extends into thebody 171, for instance into the upper surface 183 a toward the lowersurface 183 b (See FIG. 5D). The aperture 190 can further extend intoone or both sides 175, such that bone growth promoting material can beadded into the aperture 190, for instance in the upper surface 183 a,once the implant 170 has been inserted into the implant receiving space46. The bone growth promoting material can thus extend into the sides175 within the aperture 190 so as to contact the opposed surfaces of theposterior arch that define the implant receiving space 46. For instance,the leading end 173 a defines a length that is less than that of thetrailing end 173 b in accordance with the illustrated embodiment.

As shown in FIG. 5D, the implant can further include at least one toothsuch as a plurality of teeth 179 that project out from the implant body171, and in particular project out from the sides 175 and are configuredto abut and enhance contact with the surfaces of the posterior arch thatat least partially define the implant receiving space 46. Alternatively,the implant 170 can be inserted into an implant receiving space 46 ofthe type described above. Accordingly, after the implant 170 has beenimplanted and the other tools of the posterior arch expansion systemhave been removed, the implant 170 maintains the implant receiving space46 at a width substantially equal to the width of the implant 170 thatis configured to relieve impingement into the spinal canal. The implantcan further define a lip 191 that overhangs at least one of up to all ofthe sides 175, the leading end 173 a, and the trailing end 173 b, andabuts the an outer surface of the posterior arch portion 26 when theimplant body 171 is fully inserted in the implant receiving space 46.

Referring now to FIGS. 5A-5C, the implant 170 can alternatively oradditionally include at least one such as two mating members 187 thatproject out one or both sides 175 of the implant body 171. The matingmembers 187 can be substantially dome-shaped or any suitable alternativeshape as desired. The mating members 187 are configured to engage arespective rail 206 of the first and second arms 196 and 200 such thatthe implant 170 rides along the rails 206 as the implant is beingadvanced by the elongate pusher. Additionally, the mating members 187can act as locking protrusions to lock the implant in the implantreceiving space 46. Accordingly, a complementary aperture can be formed(e.g., cut) into, but not through, the posterior arch portion 26 atlocations that are configured to receive and capture the mating members187 of the implant 170 when the implant 170 is inserted into the implantreceiving space 46.

In operation and in reference to FIGS. 6A-6E, the access assembly 59 andin particular the cannula 70 is positioned such that the distal end 73of the cannula 70 is proximate to the first portion of the lamina 38.The cutting tool system 98 can then be advanced through the passageway75 of the cannula 70 toward the first portion 62 of the lamina 38. Byactivating the cutting tool system 98, the cutting tool system 98 cancut at least part way through the first portion 62 of the lamina 38 toform the hinge 54. Once the hinge 54 is formed, the access assembly 59and in particular the cannula 70 can be positioned such that the distalend of the cannula 70 is proximate to the second portion 66 of thelamina 38 as shown in FIG. 6B. The cutting tool system 98 can then beadvanced through the passageway 75 of the cannula 70 toward the secondportion 66 of the lamina 38. By activating the cutting tool system 98,the cutting tool system 98 can cut completely through the second portion66 of the lamina 38 to thereby form the implant receiving space 46.

Now in reference to FIGS. 6C-6E, the inserter tool 180 with the implant170 coupled to the inserter tool 180 can be is inserted into andadvanced through the passageway of the cannula 70. The implant 170 canbe coupled to the inserter tool 180 by engaging the mating members 187of the implant 170 with the rails 206 of the first and second arms 196and 200. As the inserter tool 180 is advanced further through thepassageway 75 the engagement portions 203 of the arms 196 and 200 of thespreading device 192 engage the implant receiving space 46 of the lamina38. By activating the pusher 184 so as to advance the implant 170 towardthe implant receiving space 46, the implant 170 will contact and forceor otherwise urge the arms 196 and 200 away from each other to therebyspread the implant receiving space 46 and expand the lamina 38, suchthat the implant receiving space 46 is moved from a first positionwhereby a distance measured between the opposed posterior arch surfaceshas a first width, to a second position whereby the distance measuredbetween the opposed posterior arch surfaces increases to a second width.As the implant 170 is advanced further, the implant receiving space 46will spread to a size such that the implant 170 is placed within theimplant receiving space 46 to thereby maintain the lamina 38 in itsexpanded or widened position. As will be described, the implantreceiving space 46 may be further expanded or otherwise widened byexpanding the implant 170 if the implant 170 is expandable. In suchcases, the implant receiving space can be moved from a first position toa second position, whereby a distance between the posterior archsurfaces is increased, and then subsequently moved to a third positionupon expansion of the implant whereby the distance between the posteriorarch surfaces is further increased.

Finally, the inserter tool 180 can be disengaged from the implant 170and removed from the cannula 70. As shown in FIG. 6E, the implant 170may then be secured to the lamina 38 by having the mating members 187 ofthe implant 170 engage opposed cutouts in the lamina or with screws orother fastening devices. Because the procedure is performed using onlythe access path provided by the access assembly 59, the entire procedureis minimally invasive. Therefore, through an entirely minimally invasiveprocedure, a patient's lamina 38 may be expanded or otherwise widenedfrom a first position to a second position so as to increase the size ofthe spinal canal and relieve the pressure on the patient's spinal cord.

It should be appreciated that the posterior arch expansion can becompleted by cutting through the spinous process 42 as shown for examplein FIG. 1D or by cutting two implant receiving spaces into the laminafor as shown in FIG. 1C. Such posterior arch expansion methods can beperformed using similar methodology or steps as described in conjunctionwith FIGS. 6A-6E.

Now referring to FIGS. 7A-7C, the cutting tool system 98 can includeother configurations that are configured to cut either part way through,or fully through the posterior arch portion 26. For example, the cuttingtool system 98 can include a cutting tool that is provided as a mill asdescribed above, an ultrasonic cutting tool 210 as shown in FIG. 7A, awire saw 220 as shown in FIG. 7B, or a rib cutter 230 as shown in FIG.7C. While the cutting tool system 98 has been described in accordancewith certain embodiments, it should be appreciated that the posteriorarch expansion system can include any alternative cutting toolassemblies suitable to cut a portion of the posterior arch.

Referring to FIG. 7A, the ultrasonic cutting tool 210 includes anelongate body 234 having a cutting tip 238. By applying ultrasonicshockwaves to the cutting tool 210, the cutting tip 238 will vibraterapidly and cut through the posterior arch portion 26. As with thecutting tools shown in FIGS. 3A and 3B, the ultrasonic cutting tool 210should be configured to fit within the tube 70. In operation, theultrasonic cutting tool 210 is advanced toward the posterior archportion 26 within the passageway of the tube 70 until the cutting tip238 is abutting the posterior arch portion 26. When the ultrasoniccutting tool 210 is activated, the vibrating tip 238 will cut throughthe posterior arch portion 26.

Referring to FIG. 7B, the wire saw 220 includes a length of wire 242having an abrasive surface 246. In operation, the wire 242 is advancedtoward the posterior arch portion 26 through the passageway of the tube70 to a location that is proximate to the posterior arch portion 26. Thewire 242 is then threaded around the posterior arch portion 26 and backup the cannula 70 such that both ends of the wire 242 are extendingproximally from the cannula 70. By oscillating the wire 242 back andforth, the abrasive surface 246 of the wire 242 will cut through theposterior arch portion 26.

Referring to FIG. 7C, the rib cutter 230 includes a body 250 having acutting portion 254 at its distal end. The cutting portion 254 includesa distal sharp edge 258, a pusher 262 and a gap 266 defined between theedge 258 and the pusher 262. As shown, the sharp edge is curved andextends proximally toward the pusher 262, and the pusher 262 isconfigured to translate toward the sharp edge 258. In operation, the ribcutter 230 will be advanced down the tube 70 toward the posterior archportion 26. The cutting portion 254 will be positioned such that theposterior arch portion 26 is received within the gap 266 with the sharpedge 258 abutting the back surface of the posterior arch portion 26 andthe pusher 262 abutting the front surface of the posterior arch portion26. Once properly positioned, the pusher 262 is translated forward toforce the posterior arch portion 26 against the sharp edge 258. Withfurther translation, the sharp edge 258 will cut through the posteriorarch portion 26.

The posterior arch expansion system and in particular the implantassembly 181 can include any suitable implant that is configured to beadvanced through a minimally invasive access path, such as through theaccess member 70, that provides the access path to the posterior archportion 26, and expand the posterior arch. Because the implant orimplants can be advanced down the access member 70, the fixationprocedure can be referred to as minimally invasive. To place theimplants within the implant receiving space 46 of the posterior arch,the implants may be inserted using the inserter tool 180 and spreadingdevice 192 so as to widen the implant receiving space 46 duringinsertion, or the implants may have a first width when they are beinginserted into the implant receiving space 46, and once inserted, theimplants are expanded to a second width that is wider than the firstwidth. It should thus be appreciated that the implant alone or incombination with the spreading device can expand the implant receivingspace 46. Whether the spreading device 192 expands the implant receivingspace 46 or the implant expands the implant receiving space 46, or both,it should be appreciated that the implants are inserted into the implantreceiving space 46 using a minimally invasive procedure. Exampleimplants that can be inserted through the minimally invasive access pathsuch as the path 75 through the cannula 70 are described below. Itshould be appreciated, however, that the implant is not limited to thosedescribed, and that other configurations are envisioned.

In another embodiment and in reference to FIG. 8, the implant mayinclude an engagement member that is configured to engage the posteriorarch portion 26 by capturing outer surfaces of a respective portion ofthe posterior arch portion 26 when the implant is inserted within theimplant receiving space 46 of the posterior arch portion 26. As shown,an implant 310 includes a body 314, and a pair of engagement members 316that are each configured as a pair of wings 318 extending from opposedsides of the body 314. As shown, the implant body 314 has a width thatis configured to maintain the implant receiving space 46 in the expandedposition. Therefore, the implant 310 should be inserted using theinserter tool 180 so that the implant receiving space 46 can be widenedto allow the implant 310 to be inserted within the implant receivingspace 46 without interference from the posterior arch portion 26. Eachpair of wings 318 includes first and second wings 322, 326 that extendout from opposed edges 330 of the body 314, and away from the body 314at an angle toward the outside surfaces of the posterior arch portion26. The first and second wings 322 and 326 of each pair of wings 318,therefore define a cavity 334 that is configured to receive a respectiveportion of the posterior arch portion 26 as shown in FIG. 8. Once theimplant 310 is properly positioned within the implant receiving space 46of the posterior arch portion 26, the wings 322 and 326 of each pair ofwings 318 are fastened to the posterior arch portion 26 to therebysecurely hold the implant 310 in place.

In another embodiment and in reference to FIG. 9, the implant caninclude an engagement member that is configured to clamp down againstouter surfaces of respective portions of the posterior arch portion 26.As shown, an implant 360 includes a body 363 that is configured as ashaft 364, a first engagement member configured as a first disc 368movably attached to the shaft 364, and an opposed second engagementmember configured as a second disc 372 fixed to a distal end of theshaft 364. The shaft 364 is threaded and has a diameter D₁ that is equalto the width in which the posterior arch portion 26 is to be expanded.It should be appreciated, however, that the implant 360 could include asleeve having a diameter D₁ that is placed over the shaft 364 andbetween the first and second discs 368 and 372. In either case, theimplant 360 should be inserted using the inserter tool 180 so that theimplant receiving space 46 can be widened to allow the implant 360, orat least the shaft 364 to be inserted within the implant receiving space46 without interference from the lamina.

The shaft 364 includes threads 376 that are configured to engage threadsdefined by a bore 384 that extends through a center of the first disc368. The threaded engagement between the shaft 364 and the first disc368 allows the first disc 368 to be incrementally translated toward thesecond disc 372. As shown, the first and second discs 368 and 372include teeth 388 that extend from opposed internal surfaces 392 of thediscs 368 and 372. In operation the implant 360 is placed such the shaft364 is located within the implant receiving space 46 and the first andsecond discs 368 and 372 are located on opposed sides of the posteriorarch portion 26. Once the implant 360 is properly positioned within theimplant receiving space 46 of the posterior arch portion 26 the firstdisc 368 may be translated toward the second disc 372 until the teeth388 of the two discs 368 and 372 engage the outer surfaces of theposterior arch portion 26 to thereby clamp the implant 360 to theposterior arch portion 26. Once the teeth 388 have engaged the posteriorarch portion 26, the implant 360 is securely held in place.

In another embodiment and in reference to FIGS. 10A and 10B, the implantmay be a rivet that clamps against the posterior arch portion 26 to holdthe implant in place. As shown, an implant 410 includes a bodyconfigured as a shaft 414, a first engagement member configured as ahead 418 and attached to a proximal end of the shaft 414, and a mandrel422 that extends through the center of both the first head 418 and theshaft 414. The shaft 414 has a diameter D₁ that is equal to the width inwhich the posterior arch portion 26 is to be expanded. Therefore, theimplant 410 should be inserted using the inserter tool 180 so that theimplant receiving space 46 can be widened to allow the implant 410, orat least the shaft 414, to be inserted within the implant receivingspace 46 without interference from the posterior arch portion 26.

In operation, the implant 410 is placed such that the first head 418abuts the outer surfaces of the posterior arch portion 26, and amajority of the shaft 414 extends into the implant receiving space 46,with a portion 426 of the shaft 414, known as the blind end, protrudinginto the spinal canal. Once properly positioned, the mandrel 422 isdrawn proximally to thereby expand the portion 426 of the shaft 414within the spinal canal, and create a second engagement memberconfigured as a head 430 that abuts the posterior arch portion 26 withinthe spinal canal, as shown in FIG. 10B. The first and second heads 418and 430 clamp the implant 410 to the posterior arch portion 26 tothereby securely hold the implant 410 in place.

The implant can also be configured to expand along a direction that istransverse to the direction in which the implant is inserted into theimplant receiving space. That is, if the implant is in inserted into theimplant receiving space along an insertion direction, the implant canthen be subsequently expanded along an expansion direction that istransverse to, such a substantially perpendicular to, the insertiondirection. FIGS. 11A-19B disclose several embodiments of an implant thatcan expand from a first or compressed configuration or position to asecond or expanded configuration or position.

For example and in reference to FIGS. 11A and 11B, the implant caninclude a body that is configured to expand from a first or compressedconfiguration or position to a second or expanded configuration orposition, thereby expanding the implant receiving space after theimplant has been implanted. For instance, referring to FIG. 11A, animplant 450 includes an expandable body 454, and a respective engagementmember 455 that extends from opposed ends of the body 454. Theexpandable body 454 includes a first threaded member 456 that extendsfrom a first engagement member 455 and a second threaded member 457 thatextends from a second engagement member 455. The first threaded member456 includes left handed threads while the second threaded member 457includes right handed threads. The second threaded member 457 furtherdefines an internal bore 470 that is configured to receive the firstthreaded member 456 when the implant is in the compressed configurationor position. The expandable body 454 further includes an expansionmechanism 458 that defines a threaded bore 459. Each of the first andsecond threaded members 456 and 457 engage an opposed end of thethreaded bore 459 such that rotation of the expansion mechanism 458causes the first and second threaded members 456 and 457 to translateaway from each other. As shown, when the expansion mechanism 458 isactuated both the implant 450 and the implant receiving space expandfrom an initial first width W₀, as shown in FIG. 11A, to an expandedsecond width W₁, as shown in FIG. 11B.

The body 454 further defines first and second opposed bone contactingsurfaces 466 a and 466 b that are configured to engage the first andsecond posterior arch surfaces. When the body 454 is expanded from thefirst width to the second width, the first and second bone contactingsurfaces 466 a and 466 b urge against the first and second posteriorarch surfaces to thereby expand or otherwise widen the implant receivingspace 46.

The engagement members 455 may have a variety of configurations so longas they are capable of engaging the lamina to thereby hold the implant450 in place. For example, the engagement members 455, in theillustrated embodiment include fixation element receiving apertures 460configured to receive fixation elements such as bone screws. The screwswill engage the lamina to thereby fasten the implant 450 to the lamina.

In operation, the implant 450 is passed through the passageway of thecannula 70 and subsequently inserted into the implant receiving space 46while the body 454 is in the compressed configuration or position andthe implant defines the first width W₀. Once properly placed, theengagement members 455 may be fastened to the lamina with bone screwsand the expansion mechanism 458 may be actuated to allow the body 454 toexpand such that the implant 450 and the implant receiving space expandto the second width W₁. The expansion mechanism 458 can be activatedusing a tool that extends through passageway of the cannula and engagesthe expansion mechanism 458 so as to rotate the expansion mechanism. Forexample, the expansion mechanism 458 can have a rough outer surface thatallows the tool to engage the expansion mechanism to thereby rotate theexpansion mechanism.

In another embodiment and in reference to FIGS. 12A and 12B, the implantmay be expanded using an inflatable device from the first or compressedconfiguration or position to the second or expanded configuration orposition. As shown, an implant 510 includes an expandable body 514 andengagement members 518 that extend from opposed sides of the body 514.The body 514 includes a frame 522 and at least one expandable balloon526 having laterally opposed sides 526 a and 526 b that extend throughthe frame 522. The balloon 526 is configured to inflate to therebyexpand the implant 510 from a defined initial first width W₀, as shownin FIG. 12A, to an expanded second width W₁, as shown in FIG. 12B. Theballoon 526 can be inflated by injection of any suitable expansion mediainto the balloon 526. For instance, cement can be pumped through acannulated rod that is attached to the frame 522 and in fluidcommunication with the interior of the balloon.

The body 514 and in particular the opposed sides of the balloon 526 aand 526 b, further define first and second opposed bone contactingsurfaces 527 a and 527 b that are configured to engage the first andsecond posterior arch surfaces. When the body 514 is expanded from thefirst width to the second width, the first and second bone contactingsurfaces 527 a and 527 b urge against the first and second posteriorarch surfaces to thereby expand or otherwise widen the implant receivingspace 46.

The engagement members 518 may have a variety of configurations so longas they are capable of engaging the lamina to thereby hold the implant510 in place. For example, the engagement members 518, in theillustrated embodiment, each define a plate that includes fixationelement receiving apertures 530 configured to receive fixation elementssuch as bone screws. The screws will engage the lamina to thereby fastenthe implant 510 to the lamina.

In operation, the implant 510 is inserted into the implant receivingspace 46 while the body 514 is compressed and the implant 510 definesthe first width W₀. The initial first width W₀ therefore is less than orsubstantially equal to the width of the implant receiving space 46, andis accordingly small enough to allow the implant 510 to be insertedwithin the implant receiving space 46. Once properly placed, the balloon526 may be inflated to thereby expand the implant receiving space 46. Inother words, expansion of the balloon 526 expands the implant receivingspace 46 from a first width (which is substantially equal to the firstwidth W₀ defined by the implant 510) to a second width (which issubstantially equal to the second width W₁ defined by the implant 510).Therefore, the implant 510 can be said to expand the implant receivingspace 46 from a first width to a second expanded width. While beinginflated, the frame 522 will orient the balloon expansion, preventing itfrom expanding against the dura and orienting it towards the lamina.Once the lamina has been expanded, the engagement members 518 may befastened to the lamina. Otherwise stated, the frame 522 defines a guidethat directs the expansion of the balloon 526 toward the lamina.

In another embodiment and in reference to FIG. 13, the implant may beconfigured to rotate to thereby expand the lamina. As shown, an implant550 includes an expandable body 554 and an engagement member 558extending from the body 554. The body 554 is oblong and includes opposedrounded corners 562. As shown, the body 554 has a height that defines aninitial first width W₀ and a length that defines a second expanded widthW₁. The second width W₁ is greater than the first width W₀. Theengagement member 558 defines a pair of opposed fixation elementreceiving apertures 566, each configured to receive a fixation elementsuch as a bone screw. The body 554 is positioned on the engagementmember 558 between the apertures 566 such that the second width W₁extends from one aperture 566 to the other aperture 566.

The body 554 further defines first and second opposed bone contactingsurfaces 567 a and 567 b that are configured to engage the first andsecond posterior arch surfaces. When the body 554 is expanded from thefirst width to the second width, the first and second bone contactingsurfaces 567 a and 567 b urge against the first and second posteriorarch surfaces to thereby expand or otherwise widen the implant receivingspace 46.

In operation, the implant 550 is inserted into the implant receivingspace 46 while in the first configuration or position such that the body554 is oriented to have its first width W₀ within the implant receivingspace 46. The initial first width W₀ therefore is less than orsubstantially equal to the width of the implant receiving space 46, andis accordingly small enough to allow the implant 550 to be insertedwithin the implant receiving space 46. By rotating the implant 550 90degrees, the implant will be in the second configuration or positionsuch that the body will be oriented to have its second expanded width W₁within the implant receiving space 46. The rounded corners 562 of thebody 554 allow the implant 550 to more easily force the opposed laminaportions apart. As shown, the expanded second width W₁ should be equalto the width in which the posterior arch portion 26 is to be expanded.Therefore, the implant 550 can be said to expand the implant receivingspace 46 from a first width to a second expanded width.

In another embodiment and in reference to FIGS. 14A and 14B, the implantmay be configured to expand upon rotation of a wrench from the first orcompressed configuration or position to the second or expandedconfiguration or position. As shown, an implant 570 includes a body 571having first and second frames 572, and 574 that are connected by firstand second members 576 and 578. As shown, each frame 572 and 574 definesan elongate channel 580 and a bore 582. The implant 570 further includesa respective engagement member 584 that extends from each frame 572 and574. Each engagement member 584 defines a pair of fixation elementreceiving apertures 586 configured to receive screws to thereby fastenthe implant 570 to the lamina. Each member 576 and 578 includes arespective elongate body 579 and 581 and first and second transverserods 588 a and 588 b that extend outward from opposed ends of theelongate bodies 579 and 581. The first transverse rod 588 a of the firstmember 576 extends into the bore 582 of the first frame 572, and thesecond transverse rod 588 b of the first member 576 extends into thechannel 580 of the second frame 574. Similarly, the first transverse rod588 a of the second member 578 extends into the bore 582 of the secondframe 574, and the second transverse rod 588 b of the second member 578extends into the channel 580 of the first frame 572. The implant 570 canfurther include a transversal pin 583 that pivotally connects members578 and 576 at a joint 585. During use, the first and second members 576and 578 are pivotal with respect to the frames 572 and 574, respectivelyabout their respective first transverse rods 588 a, and are furtherconfigured to translate with respect to the frames 578 and 576,respectively, as their respective second transverse rods 588 b ridealong the complementary channels 580.

The implant 570 further includes a wrench 590 having a threaded member592 that extends through a longitudinal threaded bore 594 of the firstframe 572. As shown, the threaded member 592 is coupled to an end of thesecond member 578. As the wrench 590 is rotated, the threaded member 592will translate into the first frame 572 and push the end of the secondmember 578. As the second member 578 is pushed, the rods 588 of themembers 576 and 578 translate within their respective channels 580, andthe members 576 and 578 rotate about their respective other rods 588 tothereby expand the implant 570. The pin 583 allows the rotation of eachmember 576 and 578 is equal, and both engagement members 584 translatesubstantially parallel to each other. As shown, the implant 570 mayexpand from an initial first width W₀, as shown in FIG. 14A, to anexpanded second width W₁, as shown in FIG. 14B.

The body 571 and in particular the first and second frames 572 and 574further define first and second opposed bone contacting surfaces 598 aand 598 b that are configured to engage the first and second posteriorarch surfaces. When the body 571 is expanded from the first width to thesecond width, the first and second bone contacting surfaces 598 a and598 b urge against the first and second posterior arch surfaces tothereby expand or otherwise widen the implant receiving space 46.

In operation, the implant 570 is inserted into the implant receivingspace 46 such that the frames 572 and 574 are collapsed and the implant570 defines the first width W₀. The initial first width W₀ therefore isless than or substantially equal to the width of the implant receivingspace 46, and is accordingly small enough to allow the implant 570 to beinserted within the implant receiving space 46. Once the implant 570 ispositioned and affixed to the lamina, the implant may be expanded to theexpanded configuration or position. Therefore, by rotating the wrench590, the frames 572 and 574 move away from each other to thereby expandthe implant 570 such that the implant 570 defines the second width W₁.As shown, the expanded second width W₁ should be equal to the width inwhich the posterior arch portion 26 is to be expanded. Therefore, theimplant 570 can be said to expand the implant receiving space 46 from afirst width to a second expanded width.

In another embodiment and in reference to FIGS. 15A and 15B, the implantmay be deformable from the first configuration or position to the secondconfiguration or position. As shown, an implant 602 may include anexpandable body 604 that defines an O-ring. The body 604 is made from amaterial that is capable of deforming. The implant 602 further includesopposed engagement members 606 that extend from the body 604. One of theengagement members 606 defines a fixation element receiving aperture608, and the other engagement member 606 defines two fixation elementreceiving apertures 608. As shown in FIG. 15A, the body 604 initiallydefines an O-shape such that the implant 602 defines an initial firstwidth W₀. As shown in FIG. 15B, the body 604 may be flattened orotherwise deformed to expand such that the implant 602 defines a secondexpanded width W₁.

In operation, the implant 602 is positioned and loosely affixed to thelamina by inserting a screw through bore 608 of the engagement member606. The implant 602 is then rotated and positioned such that the otherengagement member 606 may affixed to the lamina with second and thirdscrews. Once the implant 602 is securely fastened to the lamina, thebody 604 may flattened or otherwise deformed to thereby expand theimplant and thus the lamina. Therefore, the implant 602 can be said toexpand the implant receiving space 46 from a first width to a secondexpanded width.

As shown in FIG. 16, the posterior arch portion 26 may be cut such thatthe posterior arch surfaces have other configurations. For example,posterior arch surfaces or the implant receiving space 46 can define twoopposed keel cuts in the posterior arch portion 26. In particular, theimplant receiving space 46 may include a first keel cut 609 defined in afirst side 610 a of the implant receiving space 46, and a second keelcut 611 defined in an opposed second side 610 b of the implant receivingspace 46. The first and second keel cuts 609 and 611 may be configuredto receive first and second keels of an implant. It should beappreciated that the posterior arch surfaces can also define teeth orsteps, for example.

In that regard, and in reference to FIGS. 17A and 17B, the implant mayinclude keels that securely hold the implant within the implantreceiving space 46 of the posterior arch portion 26. As shown, animplant 612 includes an expandable body 614 that defines a cavity 618,and includes a rotating member 622 mounted within the cavity 618 of thebody 614. The body 614 further includes opposed first and second bodyportions 626 and 628 that are each configured to engage respectiveportions of the posterior arch portion 26. Each body portion 626 and 628defines an internal surface 630 and an outer surface 634. Each bodyportion 626 and 628 of the body 614 further includes ratchet teeth 638that extend from their respective internal surfaces 630 and toward theother body portion 626 and 628 of the body 614. The ratchet teeth 638 ofthe first body portion 626 have an engagement surface 642, while theratchet teeth 638 of the second body portion 628 have an engagementsurface 642 that is opposite to the engagement surface of the first bodyportion 626. In other words, the engagement surfaces 642 of the firstbody portion's 626 ratchet teeth are angled in a first direction, whilethe engagement surfaces 642 of the second body portion's 628 ratchetteeth are angled in a second direction that is opposite to the firstdirection. Each body portion 626 and 628 further includes an engagementmember defined as a keel 646 that extends from its respective outersurface 634. The keels 646 are configured to engage keel cuts such askeel cuts 609 and 611 shown in FIG. 14 and therefore can be said todefine engagement members.

The rotating member 622 includes a body 650 having a length L andopposed first and second angled ends 654 and 656. The ends 654 and 656include ratchet teeth 658 having an engagement surface 662. As shown,the engagement surfaces 662 of the first end's 654 ratchet teeth 658 areangled in a first direction, while the engagement surfaces 662 of thesecond end's 656 ratchet teeth 658 are angled in a second direction thatis opposite to the first direction. The rotating member 622 isconfigured to rotate through at least an arc of 90 degrees from a firstposition in which the implant 612 defines an initial first width W₀, toa second expanded position in which the implant 612 defines an expandedsecond width W₁.

The body 614 and in particular the first and second body portions 626and 628 further define first and second opposed bone contacting surfaces666 a and 666 b that are configured to engage the first and secondposterior arch surfaces. When the body 614 is expanded from the firstwidth to the second width, the first and second bone contacting surfaces666 a and 666 b urge against the first and second posterior archsurfaces to thereby expand or otherwise widen the implant receivingspace 46.

In operation, the implant 612 is inserted into the implant receivingspace 46 while the rotating member 622 is in the first position and theimplant 612 defines the first width W₀. The initial first width W₀therefore is less than or substantially equal to the width of theimplant receiving space 46, and is accordingly small enough to allow theimplant 610 to be inserted within the implant receiving space 46. Onceproperly placed, the keels 646 are engaged with the first and secondkeel cuts 609 and 611, and the rotating member 622 may be rotated to itssecond position, so as to allow the body 614 to expand such that theimplant 612 defines the expanded second width W₁. As the rotating member622 is rotated (counter clockwise for the embodiment shown), theengagement surfaces 662 of the first end's ratchet teeth 658 are forcedagainst the engagement surfaces 642 of the first body portion's ratchetteeth 638, and the engagement surfaces 662 of the second end's ratchetteeth 658 are forced against the engagement surfaces 642 of the secondbody portion's ratchet teeth 638. As the rotating member 622 is furtherrotated, the ratchet teeth of the rotating member 622 and the ratchetteeth of the body portion's 626 and 628 engage each other to therebyforce the body portion's 626 and 628 apart. Once fully apart, theratchet teeth lock the implant in the expanded second position whichdefines the second width W₁. As shown, the expanded second width W₁should be equal to the width in which the posterior arch portion 26 isto be expanded. Therefore, the implant 612 can be said to expand theimplant receiving space from a first width to a second expanded width.

In another embodiment and in reference to FIGS. 18A and 18B, the implantmay include rotating members coupled to both body portions and areconfigured to expand the implant upon translation of one of the bodyportions relative to the other. As shown, an implant 710 include a body713 having a first body portion 714, an opposed second body portion 718and at least two rotatable members 722 rotatably coupled or hinged tothe first and second body portions 714 and 718. As shown, each bodyportion 714 and 718 includes a keel 726 that extends out from an outersurface of a respective body portion 714 and 718. The keels 726 areconfigured to engage the keel cuts 609 and 611 formed in the implantreceiving space 46 of the posterior arch portion 26 and therefore can besaid to define engagement members. The members 722 are each rotatablycoupled to the first and second body portions 714 and 718 proximate toopposed ends of the body portions 714 and 718 at respective first andsecond pivots 728 and 730. The implant 710 is configured to expand froman initial first width W₀, to an expanded second width W₁, by rotatingthe first body portion 714 counter clockwise.

The body 713 and in particular the first and second body portions 714and 718 further define first and second opposed bone contacting surfaces731 a and 731 b that are configured to engage the first and secondposterior arch surfaces. When the body 713 is expanded from the firstwidth to the second width, the first and second bone contacting surfaces731 a and 731 b urge against the first and second posterior archsurfaces to thereby expand or otherwise widen the implant receivingspace 46.

In operation, the implant 710 is inserted into the implant receivingspace 46 while the implant 710 is in its first position and defines thefirst width W₀. The initial first width W₀ therefore is less than orsubstantially equal to the width of the implant receiving space 46, andis accordingly small enough to allow the implant 710 to be insertedwithin the implant receiving space 46 without first expanding theimplant receiving space 46 using the inserter tool 180. Once properlyplaced, the first body portion 714 may be rotated to its secondposition, so as to allow the implant 710 to expand to the expandedsecond width W₁. As shown, the expanded second width W₁ should be equalto the width in which the posterior arch portion 26 is to be expanded.Therefore, the implant 710 can be said to expand the implant receivingspace from a first width to a second expanded width.

In another embodiment and in reference to FIGS. 19A and 19B, the implantmay include a deformable body that is locked in a compressed positionwith a locking pin. As shown, an implant 810 includes a deformable body814 and a pair of engagement members 818 that extend from opposed endsof the body 814. As shown in FIGS. 19A and 19B the body 814 initiallydefines an oblong ring having a bore 822 that extends therethrough. Thebody 814 further includes a pair of protrusions 826 that extend upwithin the bore 822 such that a recess 830 is defined between theprotrusions 826, and a third protrusion 834 that opposes the protrusions826 such that third protrusion 834 extends into the recess 830 when thebody 814 is in a compressed configuration or position as shown in FIG.19A. Each of the protrusions 826 and 834 defines a bore 838 that areconfigured to be aligned. The body 814 further includes a locking pin842 that is configured to engage the bores 838 when the body 814 is inthe compressed configuration or position to thereby hold the implant inthe first or compressed configuration or position.

The body 814 further defines first and second opposed bone contactingsurfaces 843 a and 843 b that are configured to engage the first andsecond posterior arch surfaces. When the body 814 is expanded from thefirst width to the second width, the first and second bone contactingsurfaces 843 a and 843 b urge against the first and second posteriorarch surfaces to thereby expand or otherwise widen the implant receivingspace 46.

The engagement members 818 may have a variety of configurations so longas they are capable of engaging the lamina to thereby hold the implant810 in place. For example, the engagement members 818, in theillustrated embodiment, each define a keel that includes a fixationelement receiving aperture 840 configured to receive a fixation elementsuch as a bone screw. The screws will engage the lamina to therebyfasten the implant 810 to the lamina.

In operation, the implant 810 may be implanted into the implantreceiving space 46 of the lamina while in a compressed position suchthat the implant 810 defines a first width W₀ as shown in FIG. 19A. Onceinserted, screws may be inserted through the bores 840 of the engagementmembers 818 and into the lamina to thereby affix the implant 810 to thelamina. The locking pin 842 may then be removed to thereby allow thebody 814 and thus the implant receiving space 46 to expand to anexpanded position such that the implant 810 and the implant receivingspace 46 each defines a second expanded width W₁ as shown in FIG. 19B.Therefore, the implant 810 can be said to expand the implant receivingspace 46 from a first width to a second expanded width.

In another embodiment and in reference to FIG. 20, the implant mayinclude stops to prevent the implant from falling into the spinal canalduring insertion. As shown, an implant 880 includes a body 884 havingstops 888 that extend up from a surface of the body 884. The stops 888are configured to contact the posterior arch portion 26 to preventfurther insertion and avoid over insertion of the implant.

In another embodiment and in reference to FIG. 21, the implant may be apaddle plate. As shown, an implant 910 includes a plate 914 and athreaded screw 918 extending from an end of the plate 914. The plate 914is substantially flat and defines a plurality of fixation elementreceiving apertures 922. While the plate 914 is shown as being flat, itshould be understood that the plate 914 may be pre-curved or bent toadapt to the lamina shape.

In operation, the screw 918 is threaded into the lamina such that theplate 914 extends across the face of the implant receiving space 46.Using additional instrumentation such as pliers, the lamina is expanded.While expanded, screws may be inserted through the apertures 922 of theplate 914 and into the lamina to thereby affix the implant 910 to thelamina.

In another embodiment and in reference to FIG. 22, the implant may be apaddle plate with a hinge. As shown, an implant 950 includes a body thatdefines a plate 954, and further includes a threaded screw 958 extendingfrom an end of the plate 954. The plate 954 is initially substantiallyflat and defines a plurality of fixation element receiving apertures962. As shown, the plate 954 further defines a plurality of hinges 976that allow the plate to be bent to create a hinged portion 980. Asshown, the hinged portion 980 is configured to rotate about one of thehinges 976.

In operation, the implant 950 is inserted into the opening to assess thebest position to bend the plate 954. Once determined the implant isremoved and the plate 954 is bent about one of the hinges 976 to betterfit the anatomy. The implant may then be reinserted into the opening andthe screw 958 may be threaded into the lamina such that the plate 954extends across the face of the implant receiving space 46. Using anspreading device such as pliers, the lamina is expanded. While expanded,screws may be inserted through the apertures 962 of the plate 954 andinto the lamina to thereby affix the implant 950 to the lamina.

Now referring to FIGS. 23A and 23B, the implant assembly can includeother configurations for inserting the implant. As shown, an implantassembly 1000 can include an inserter tool 1004 and an implant 1008coupled to the inserter tool 10004. The inserter tool 1004 includes anelongate shaft 1012 and a coupler 1016 at a distal end of the shaft1012. The coupler 1016 includes an external thread 1020 that isconfigured to engage internal threads defined by the implant 1008.Therefore, the implant receiving space 46 can be widened with aspreading device and the inserter tool 1004 can implant the implant 1008into the widened implant receiving space 46. Once implanted, theinserter tool 1004 can be decoupled from the implant 1008. It should beappreciated that the coupler 1016 can include other configurations toreleasably couple the inserter tool 1004 to the implant 1008. Forexample, the coupler 1016 can be a clip. The inserter tool 1004 can alsobe coupled to an expandable implant such as those shown in for example,FIGS. 11A, 12A, and 13. In such cases the implant receiving space can bewidened, before, during, or even after implantation of the implant intothe implant receiving space.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. Furthermore, it should be appreciated thatthe structure, features, and methods as described above with respect toany of the embodiments described herein can be incorporated into any ofthe other embodiments described herein unless otherwise indicated. Forexample, any of the implants described can include mating members asshown in FIG. 5A or engagement members to thereby couple the implant tothe lamina. It is understood, therefore, that this invention is notlimited to the particular embodiments disclosed, but it is intended tocover modifications within the spirit and scope of the presentdisclosure.

What is claimed:
 1. A minimally invasive method of expanding a spinalcanal, the method comprising the steps of: forming a minimally invasiveaccess path to a posterior arch portion of a vertebra; cutting animplant receiving space in the posterior arch portion of the vertebra byinserting a cutting tool system through the minimally invasive accesspath, the implant receiving space defined between opposed posterior archsurfaces; advancing an implant coupled to an inserter tool through theminimally invasive access path and toward the implant receiving space;inserting the implant into the implant receiving space, the insertingstep comprising: causing engagement portions of first and second arms ofthe inserter tool to engage the opposed posterior arch surfaces;advancing the implant between the first and second arms such that (1) atleast one mating member that extends out from a side of the implantrides within a rail of one of the first and second arms, (2) the implanturges the first and second arms away from each other, and (3) theengagement portions of the first and second arms urge the opposedposterior arch surfaces away from one another to thereby expand theimplant receiving space such that a distance measured between theposterior arch surfaces increases from a first width to a second widththat is greater than the first width.
 2. The method of claim 1, whereinexpanding the implant receiving space occurs as the implant is beinginserted into the implant receiving space.
 3. The method of claim 1,wherein expanding the implant receiving space occurs before the implantis inserted into the implant receiving space.
 4. The method of claim 1,wherein comprising a step of expanding the implant receiving space afterthe implant is inserted into the implant receiving space.
 5. The methodof claim 4, wherein the step of expanding the implant receiving spaceafter the implant is inserted comprises a step of expanding the implant.6. The method of claim 5, wherein the step of expanding the implantincludes rotating the implant.
 7. The method of claim 5, wherein thestep of expanding the implant includes deforming an expandable body ofthe implant.
 8. The method of claim 5, wherein the step of expanding theimplant includes inflating a balloon.
 9. The method of claim 5, whereinthe step of expanding the implant includes rotating a rotatable memberof the implant.
 10. The method of claim 5, wherein the step of expandingthe implant includes activating an activation mechanism.
 11. The methodof claim 1, further comprising the step of forming a hinge in theposterior arch portion of the vertebra with the cutting tool system. 12.The method of claim 1, wherein the step of cutting the implant receivingspace includes cutting through the posterior arch portion of thevertebra.
 13. The method of claim 1, wherein the posterior arch portionis a spinous process.
 14. The method of claim 1, wherein the step offorming the minimally invasive access path comprises positioning acannula such that a distal end of the cannula is proximate to theposterior arch portion of the vertebra, the cannula having an elongatebody and a passageway that extends through the body toward the posteriorarch portion of the vertebra, the passageway defining the minimallyinvasive access path to the posterior arch portion of the vertebra. 15.The method of claim 14, wherein the step of forming the minimallyinvasive access path includes positioning the cannula proximate to avertebra of the cervical spine, and the passageway has a cross-sectionaldimension that is between about 10 mm and about 25 mm.
 16. The method ofclaim 14, wherein the step of forming the minimally invasive access pathincludes positioning the cannula proximate to a vertebra of the lumbarspine, and the passageway has a cross-sectional dimension that isbetween about 15 mm and about 50 mm.
 17. The method of claim 1,comprising a step of forming an aperture in one of the opposed posteriorarch surfaces, and the step of inserting the implant comprises insertingthe mating member in the aperture.
 18. The method of claim 1, whereineach of the at least one mating member is a domed protrusion, and theadvancing step comprises advancing the implant such that the domedprotrusion rides within a rail of one of the first and second arms. 19.The method of claim 10, wherein each of the at least one mating memberis a protrusion having a curvature in a first plane, and a curvature ina second plane, perpendicular to the first plane, and the advancing stepcomprises advancing the implant such that the protrusion rides within arail of one of the first and second arms.
 20. The method of claim 1,wherein the advancing step comprises advancing the implant such that atrailing end of the implant trails a leading end of the implant, thetrailing end having a width between the first and second arms that isgreater than a width of the leading end between the first and secondarms.